1. Field of the Invention
The present invention relates to stand apparatuses for medical optical instruments and, more particularly, to a stand apparatus for medical optical instrument, which is particularly low in center of gravity and in which an attempt can be made to effectively utilize an upper space.
2. Description of the Prior Art
Local operation of an affected or diseased part in cerebral surgical operation and heart surgical operation is executed while observing the affected part by an operation microscope which serves as "Medical Optical Instrument", and is generally called "microsurgery". Operation of this kind or type is difficult among various operations, and there are many cases where operation time is lengthened. It is not preferable for a patient and a doctor or a physician, however, that the operation time is lengthened in this manner, because a fatigue increases bodily and mentally. Accordingly, a social demand or request increases more and more in which an attempt can be made to reduce or shorten such operation time.
The medical optical instrument such as the operation microscope or the like performs extremely large duties in such high operation. In fact, it is said that easiness of the use of the medical optical instrument is linked to shortening of the operation time as it is.
That is, it becomes a very important point in an attempt to shorten the operation time how an operator can accurately and speedily or rapidly position the medical optical instrument to a desired objective point (target affected part), and that the once fixed objective point does not shift during operation. In view of this, although the easiness of the use of the medical optical instrument is said, a problem results from, rather than the performance of the medical optical instrument per se, after all, operability of a stand apparatus which supports the medical optical instrument.
In view of the above, an inventor of the present application has provided, until now, a stand apparatus superior in operability, which can contribute to shortening of the operation time (refer to Japanese Patent Laid-Open No. SHO 64-56409, i.e. U.S. Pat. No. 4,881,709). FIG. 5 and 6 of the attached drawings are views showing an example of a conventional stand apparatus of the kind referred to above. In this connection, as a directionality in the drawings, the reference character A denotes a front side; B, a rear side; C, a left-hand side; D, a right-hand side; E, an upper side; and F, a lower side.
The stand apparatus comprises a front-side parallel link mechanism 2 supporting an operation microscope 1, a rear-side parallel link mechanism 3 supporting a counterweight W, and a supporting body 4 supporting both the front- and rear-side parallel link mechanisms 2 and 3. FIG. 5 is an outer appearance view showing an entire arrangement of the stand apparatus, while FIG. 6 is a diagram showing only the front- and rear-side parallel link mechanisms 2 and 3 of the stand apparatus. The conventional stand apparatus will hereunder be described on the basis of FIG. 6 which is easy to be understood in structure or construction and operation.
A central portion between the front-side parallel link mechanism 2 and the rear-side parallel link mechanism 3 is a center shaft S1. The center shaft S1 is supported by a bearing section 5 which is supported at a predetermined height position by first and second horizontal arms 6 and 7 of the support body 4. The center shaft S1 can execute rotational or angularly moving operation about an axis a1, and can also execute seesaw operation (both front and rear ends being swingable upwardly and downwardly) about an axis .alpha.2 of the bearing section 5.
Further, a longitudinal frame T is supported for angular movement about an attaching point 8 at a location in the neighborhood of the bearing section 5 of the center shaft S1. A portion of the center shaft S1 in front of the attaching point 8 and an upper portion of the longitudinal frame T are utilized to form the front-side parallel link mechanism (parallelogrammatic link structure or construction) 2, while a portion of the center shaft S1 in rear of the attaching point 8 and a lower portion of the longitudinal frame T are utilized to form the rear-side parallel link mechanism (parallelogrammatic link construction) 3. The operation microscope 1 that is a supporting object is supported at a forward end of the front-side parallel link mechanism 2. Provided on the rear-side parallel link mechanism 3 is the counterweight W which keeps a weight balance with respect to the operation microscope 1. In this connection, a curved section 2a, which is provided on the front-side parallel link mechanism 2, is provided for avoiding an interference between the front-side parallel link mechanism 2 and a head of an operator which operates the operation microscope 1.
In order to change or alter an observation angle due to the operation microscope 1, each of the front-side parallel link mechanism 2 and the rear-side parallel link mechanism 3 is capable of being inclined or tilted longitudinally about the attaching point 8. That is, as shown in FIG. 6, about the attaching point 8, the front-side link mechanism 2 can be tilted to a forward side, while the rear-side parallel link mechanism 3 can be tilted to a rear side. Accordingly, the operation microscope 1 can be positioned to every locations by rotational or angularly moving operation of the center shaft S1 about the axis .alpha.1, longitudinal tilting operation of the front- and rear-side parallel link mechanisms 2 and 3, and seesaw operation of the center shaft S1 about the axis .alpha.2. Furthermore, since a focal point f of the operation microscope 1 is located on the axis .alpha.1 which serves an extension line of the center shaft S1, even if the observation angle of the operation microscope 1 changes, an observation point is immovable.
In the conventional stand apparatus for the medical optical instrument constructed as described above, as described previously, the counterweight W, which is provided on the rear-side parallel link mechanism 3, becomes an extremely heavy article, to keep a weight balance between both the operation microscope 1 and the front-side parallel link mechanism 2. Since the counterweight W per se, which serves as the heavy weight article, largely moves longitudinally, laterally, or the like, a considerable space is required in the neighborhood of, particularly, the rear-side parallel link mechanism 3. Moreover, since both the front-side parallel link mechanism 2 and the rear-side parallel link mechanism 3 are supported at their respective predetermined height positions by the support body 4, the rear-side parallel link mechanism 3 per se, on which the counterweight W is provided, is located at a certain height position.
However, a part space upper than the height position, at which the rear-side parallel link mechanism 3 is located, is an important space for the operator and an assistant or helper. It is very inconvenience for the operator or like the that the space is occupied as a moving space of the rear-side parallel link mechanism 3 so that the space cannot be used freely. Further, it is not preferable from the viewpoint of stability of the entire stand apparatus that the heavy counterweight W moves longitudinally and laterally at the higher position.